I have a 7mm Weatherby I am thinking about sending to Christensen Arms to have the barrel wrapped. I think it might be a little bit of a gimmick but I have several customers who really like theirs. Am I missing some sort of new technology? I have one in .223 I am going to shoot this weekend, how vailid is the carbon wrapping does it really make the guns perform better than expected?

Any info would be appreciated

Aleko

From what I know about carbon-wrapping a barrel is that the barrel itself is of a smaller diameter than you'd normally have in that caliber and the carbon-fiber is used to stiffen the barrel. Carbon-fiber also is able to absorb a great deal of heat (it is used for the brake rotors in Formula Indy cars-- that's HOT!!) which allows the barrel to remain accurate when others would be too hot after a quick and numerous string of shots. The carbon is also very light in weight, another advantage in itself.

Acually, the carbon wrapped barrel can't absorb alot of heat. Carbon is not a great conductor. If fact its an insulator. The point for the indy cars is that they don't absorb the heat and stay consistent like tiles on a spaceshuttle. But we won't go there. So in a gun situation, the more metal the better absorbsion, the cooler the barrel stays. Remember from heat sink technology, its the material and surface area that counts.

I have seen alot of these carbon barrels sent off by my gunsmith and like the lightness, but don't like that heat disapation. I was looking into havign one built but decided to go with a ultralight krieger barrel. I know they can be finicky, but would like a custom ultralight.

Actually, the preceding statement isn't correct in all ways. Carbon comes in many forms -- soot for example is primarily carbon and in this form it is a very poor conductor of heat. However, the graphite form of carbon (i.e. that which is in the Christensen barrels) has a VERY high thermal transfer co-efficient.

The reason that *material* and area matter to a heatsink is that the thermal transfer co-efficient varies with different materials.

Graphite (the form of carbon in Christensen's barrels) has a very HIGH thermal transfer co-efficient -- higher than a conventional steel barrel (even though the Christensen barrels have a lot of epoxy mixed with that graphite). As a result, heat is transferred from the graphite quite rapidly and the barrel cools faster than a comparable steel one.

The only hunting scenario where this would be an advantage is probably prairie dog hunting where the ability to rapidly fire a carbon fiber barrel without over heating it would be an asset.

Not trying to start a flame war...

jpb

[ 08-22-2003, 17:42: Message edited by: jpb ]

I went out and shot the gun. I have found in most cases paper is a good indicator of performance. Outside temp was about 95 to 100 we had two types of ammo to start a basline. The little .223 had a very good scope on it but seemed not to like anything we shot down it. The goups were about 1" to 3/4" for five shots. This is not really what I was expecting. The barrel became very hot after each group of five. The gun was cleaned and allowed to cool. This took longer than expected, possibly the insulator theory may be correct. We then shot the gun with hot and cold barrels, the accuracy was in the range above. Not bab we just need some more time with the gun. As a whole I think I will stick with the Blaser. I see no real gains until we play with some differnt ammo.

Aleko

Your right in alot of ways. Carbon fiber can transfer heat great along the length of it (better than diamonds) but not perpendicular to it. Its heat trasfer coef. 1500w/mk is great along the length of it. But perpendicular to it, its like 10W/mk. Also it has to have alot of area to expell this heat at the end of the wrap or just cool by regular convection. Hence the reason for the big metal plate on the front of these barrels. What It does do I believe is spread the heat uniformly along the metal barrel. It also has alot to do with which epoxy they use. There is alot of metalic matrix epoxies out there, but very expensive. I would like to know what they use.

[ 08-23-2003, 03:42: Message edited by: bigcountry ]

Bigcountry:

Thanks for the additional information (and for being so polite). Although we have a few bad characters, this site has the highest percentage of gentlemen on the net!

jpb

Thanks, first off, I am not an expert. I am a electrical engineer, but work right beside a mechanical engineer that seems to really know this stuff working in the defense industry. I am also very curious as I have played around with the idea of carbon fibre barrels. I love my ultralights, but hate how finicky they can be with changing weather and seasons.